Variable area injector for rocket engine

ABSTRACT

A device for varying the thrust of a rocket engine either before or during flight, and for adjusting the mixture ratio easily and quickly during engine burn. A variable area fuel injector having concentric sleeves which are independently axially moveable for respectively controlling the flow of fuel and oxidizer independently of one another is provided for this purpose. These sleeves are threadably engaged with the rocket and a fixed pintle therein for permitting this axially movement.

United States Patent n 1 Spencer VARIABLE AREA INJECTOR FOR ROCKETENGINE Inventor: Duane Robert Spencer,, Redondo Beach, Calif.

The United States of America as represented by the Secretary of the NavyFiled: Apr. 26, 1971 Appl. No.: 137,633

[73] Assignee:

ms. Cl. ..60/39.74 A Int. Cl ..F02g 1/00 Field of Search ..60/258, 39.74A; 239/416,

[5 6] References Cited UNITED STATES PATENTS 3,623,319 11/1971 Schneider..60/39.74A

[ Mar. 27, 1973 3,430,863 3/1969 Canavan et a] ..60/258 3,43 L732 3/1969Lovingham et a] ..60/258 3,488,951 l/l970 Chamberlain et al. ..60/258Primary ExaminerSamuel Feinberg Att0rney-R. S. Sciascia and Thomas 0.Watson, Jr.

[ ABSIRACT A device for varying the thrust of a rocket engine eitherbefore or during flight, and for adjusting the mixture ratio easily andquickly during engine burn. A variable area fuel injector havingconcentric sleeves which are independently axially moveable forrespectively controlling the flow of fuel and oxidizer independently ofone another is provided for this purpose. These sleeves are threadablyengaged with the rocket and a fixed pintle therein for permitting thisaxially movement.

2 Claims, 1 Drawing Figure PATEHTEDMARZYIQH 3 7 2,219

INVENTOR. DUANE ROBERT SPENCER BYJL M, (7. 414a,).

ATTORNEY VARIABLE AREA INJECTOR FOR ROCKET ENGINE STATEMENT OFGOVERNMENT INTEREST The invention described herein may be manufacturedand used by or for The Government of the United States of America forgovernmental purposes without the payment of any royalties thereon ortherefor.

BACKGROUND OF THE INVENTION This invention relates to rocket engines andmore particularly relates to systems for varying the thrust of rocketengine either before or during firing A typical rocket engine comprisespropellant storage tanks, an injector, a combustion chamber, a throatregion and a nozzle. The propellants are introduced into the combustionchamber through the injector and ignited. Ignition typically occurseither by an ignitor or by hypergolic ignition. I

Propellants are usually pressurized in one of two ways. In largerengines, pumps are provided which are driven by a turbine. In smallerengines, the tanks are usually pressurized or else a separate gasgenerator is employed to pressurize the propellant.

It is often desirable in either type of propellant pressurizationsystems to have a constant thrust engine.

Thrust is directly proportional to the combustion chamber pressure,which in turn, is a function of a mass flow rate and mixture ratio ofthe propellants. Many attempts have been made to ensure constant chamberpressure.

One attempt to provide this constant chamber pressure has been theprovision of a systemof pressure regulators accurately controlling theflow rate of the propellants. The pressure regulator maintainspropellant injection into the combustion chamber at a constant ratewhich is suppose to provide constant pres sure. Disadvantages of thistype of control include a lack of compensation for variations inpropellant viscosity, particularly with cryogenics. When the viscositychanges, the mass flow rate will change which affects chamber pressure.Another disadvantage is a lack of accurate control over the mixtureratio. Pressure regulators are particularly necessary where pressurizedtanks are used because the pressure decays with depletion of propellant.Where pumps are used, it is even more difficult to control flow rate dueto the complexity and the presence of many moving parts.

Several attempts have been made to alleviate these problems. One methodemploys a hydraulic balance mechanism. In this system a piston underpressure from hydraulic fluid on one side and combustion chamberpressure on the other controls the open area of the injector. Whencombustion chamber pressure drops the hydraulic pressure moves thepiston to increase the open area of the injector. This method, whilesatisfactory in many respects, has the disadvantage of requiring preciseindependent control of the hydraulic pressure.

Another approach is to provide a spring operated sleeve which tends toclose the injector area. The spring bias is opposed by the combustionchamber pressure such that as pressure increases the injector area willdecrease. The difficulty with this type of system is that the use of alinear type spring will not provide constant pressure. That is, theforce of the spring is a function of the distance through which theSUMMARY OF THE INVENTION The purpose of this invention is to provide asystem for varying the thrust of a rocket engine. It also provides foradjustment of the mixture ratio of fuel and oxidizer. The variableadjustments allow correction of propellant flow during temperature andpressure flucuations and also minimizes the viscosity affect associatedwith gel propellants.

The system provides two concentric variably adjusta-.

ble sleeves which independently adjust the fuel flow and oxidizer flow.The inner sleeve varies space between the end of the sleeve and a pintleto adjust fuel flow. The outer sleeve varies the space between the endof the sleeve and a port to control the oxidizer flow.

OBJECTS OF THE INVENTION It is an object of the present invention toprovide a system for varying the thrust of a rocket engine.

It is a further object of the invention to allow mixture ratioadjustment of fuel and oxidizer.

Yet another object of the present invention is to provide a system whichpermits correction of propellant flow during temperature and pressureflucuations.

Still another object of the present invention is to provide a variablyadjustable system which minimizes the viscosity effect associated withdifferent propellants.

Other objects, advantages and novel features of the invention will'become apparent from the following detailed description of the inventionwhen considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a view, partially incross-section, illustrating the injector assembly employing the featuresof this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The structure shown inthe drawing represents a preferred embodiment of the novel injectorassembly. The combustion chamber and nozzle structure has been omittedfor purposes of clarification. The area shown at 10 represents thecombustion chamber. The injector assembly includes a housing 12 andcover 16 which has a threaded nipple for connecting a fuel supply line.Attached to the cover 16 is an annular pintle support 18. The concentricvariably adjustable sleeves are shown at 20 and 22 and are supportedbetween pintle support 18 and annular ring 24. Fuel flow adjustment isprovided by innersleeve 20 which is threaded at 26. The pintle support18 is likewise threaded at 26. A fixed pintle 30 is attached to pintlesupport 18 with alignment spacers provided at 32. The

the pintle 30 centered in sleeve 20. The outer sleeve 22 is threaded at34 and engages threads in annular ring 24. The threaded portions ofconcentric sleeves 20, 22 are protected from contamination by O-ringseals at 38, 39 and 40. The concentric sleeves 20, 22 have gear teeth at28 and 36 respectively and are adjusted by rotating them through geardrive mechanism and actuator shown at 42.

In operation the drive mechanism 44 rotates the inner sleeve 20 to moveit in or out to control the fuel port 48 between itself and the fixedpintle 30. Another drive mechanism rotates outer sleeve 22 to move it inor out thus adjusting the oxidizer port 50 between the sleeve 22 and thehousing 12. The number and angle of the threads 26 and 34 are determinedby the pressure, length of movement, driving torque, etc., that can bedetermined for any specific rocket engine. The drive mechanisms 44 and46 are separate and provide independent control of oxidizer and fuel.Any drive mechanism which can provide independent control of theadjustable sleeves 20 and 22 may be used.

Thus there has been disclosed an injector system which providesexcellant control of propellant flow and mixture. Obviously manymodifications and variations of the present invention are possible inthe light of the above teachings.

What is claimed is:

1. Apparatus for varying the thrust of a rocket engine comprising:

a housing;

an enlongated fixed pintle;

a first movable sleeve, having a threaded portion, concentric with andsubstantially surrounding said pintle and forming with said pintle anannular opening for injection of a first propellant;

a second movable sleeve, having a threaded portion, concentric with andof a larger diameter than said first movable sleeve and forming withsaid housing an annular opening for injection of a second propellant;and,

drive means for rotating said first and second movable sleevesindependently of each other to independently vary the area of saidannular openings.

2. The apparatus of claim 1 wherein said first movable sleeve is solid.

1. Apparatus for varying the thrust of a rocket engine comprising: ahousing; an enlongated fixed pintle; a first movable sleeve, having athreaded portion, concentric with and substantially surrounding saidpintle and forming with said pintle an annular opening for injection ofa first propellant; a second movable sleeve, having a threaded portion,concentric with and of a larger diameter than said first movable sleeveand forming with said housing an annular opening for injection of asecond propellant; and, drive means for rotating said first and secondmovable sleeves independently of each other to independently vary thearea of said annular openings.
 2. The apparatus of claim 1 wherein saidfirst movable sleeve is solid.